Helpful Answers About Foundation Repair
The staff at Foundation Sealant Systems has compiled some helpful advice about basement and chimney leaks. Browse our answers and if you still have questions, do not hesitate to contact us for more information.
Why does concrete crack?
Cracks in basement walls can develop over time due to foundation settlement, structural overload and inward pressure from expanding soils. Most basement walls will eventually develop cracks.
Why do surface repairs using hydraulic cement, caulking, and coatings or patching usually fail?
These types of repairs constantly fail within a short amount of time. Expansion and contraction movement of the wall, though minimal, causes these repairs to shadow crack and leak again.
A simple patch repair will not hold up under static pressure from the exterior. Pressure injections are permanent since the crack within the wall is completely filled and not just inside the surface.
Why use epoxy resin or polyurethane injection to repair a cracked, poured concrete basement wall?
While there are numerous ways to temporarily patch cracks, to get a permanent repair you must do two things:
- stop moisture penetration from the outside, and
- eliminate or accommodate wall movement.
Crack injection is designed for cracks in poured concrete walls. Pressure injections are done from inside the basement and the procedure will fill the crack from front to back and bottom to top, thus completely sealing the crack. Epoxy’s strength and its bond to concrete are stronger than the concrete itself.
How does crack injection work?
A two-part liquid, low viscosity liquid resin is allowed to flow under pressure into the crack in the wall from inside the basement. This resin is introduced into the crack through small ports secured over or into the crack. The resin travels all the way into the crack and then chemically reacts and solidifies – filling the space within the crack. The ports can be removed after the injection process.
How long will a crack injection repair last?
Epoxy resin will outlast concrete and is impervious to moisture.
When should epoxy be used and when should polyurethane be used?
Both polyurethane and epoxy can be used to stop water. Polyurethane has the advantage of expansion, allowing it to fill potential voids within a wall. Expansion of the polyurethane prevents the product from leaking out of the crack before it cures and thus fills the area more thoroughly. Repairs that are structural require the use of epoxy.
Does a crack in a concrete wall that is not leaking need to be repaired?
Cracks generally continue to deteriorate over time due to moisture penetration and soil pressure against walls. It is recommended that all cracks be repaired prior to finishing a basement.
I don’t have a cracked wall, but there seems to be water entering through the metal ties in the wall. Can they be repaired with epoxy resin injection?
Metal ties that were used to hold the forms together during the initial pour of the concrete can sometimes rust and allow water entry. They can be effectively repaired using epoxy resin injection.
How can I tell if the crack needs structural repair?
Signs of structural cracks include horizontal cracks, cracks 1/2” or greater, cracks that are significantly wider at the top than the bottom and offset cracks.
How can a structural fracture in a wall be repaired and the wall secured from further movement?
Most horizontal and diagonal cracks require steel angle bracing to restore structural integrity to the wall. When steel bracing is properly placed, installed and the outside soils are graded away from the house, the wall can be stabilized to prevent further movement inward.
Can a concrete crack grow?
Yes. Shrink/swell cycles in soils adjacent to the exterior of poured concrete walls, is the primary way that cracks can grow.
What if moisture remains in a crack and it freezes?
When epoxy resin or polyurethane are injected into the cracks, it will displace any moisture that may be there, minimizing the risk of frost action. Frost into the ground is gradual. Expanding saturated soils next to the exterior basement wall potentially do greater damage.
What about injecting the leaking joint between a poured concrete wall and the concrete floor slab?
The floor cove generally should not leak unless the drain tiles are blocked or non-functional. Occasionally, short distances along the cove can be injected with polyurethane to hopefully divert the water back into the drain field under the floor.
What about basement windows that are below grade and have window wells that collect groundwater and then overflow the basement?
Water gathering in window wells can be resolved by auguring a hole in the window well area down to the weeping tile and installing a perforated PVC drainpipe. The drainpipe is left empty and capped off. Clean stone is placed on the outside of the drainpipe, allowing the water that runs into the window well direct access to the weeping tile.
What about water that runs into the basement through an old chimney cleanout? How can this be repaired?
This happens when the mortar joints deteriorate from years of exposure to moisture in the ground and water runs into the chimney cavity below grade. In most cases, the repair would involve excavating around the chimney on the exterior and wrapping the chimney and concrete support with a waterproofing membrane.